Hydrocarbon-producing wells often are stimulated by hydraulic fracturing operations, wherein a servicing fluid such as a fracturing fluid or a perforating fluid may be introduced into a portion of a subterranean formation penetrated by a wellbore at a hydraulic pressure sufficient to create or enhance at least one fracture therein. Such a subterranean formation stimulation treatment may increase hydrocarbon production from the well.
When wellbores are prepared for oil and gas production, it is common to cement a casing string within the wellbore. Often, it may be desirable to cement the casing within the wellbore in multiple, separate stages. Furthermore, stimulation equipment may be incorporated within the casing string for use in the overall production process. The casing and stimulation equipment may be run into the wellbore to a predetermined depth. Various “zones” in the subterranean formation may be isolated via the operation of one or more packers, which may also help to secure the casing string and stimulation equipment in place, and/or via cement.
Following placement of the casing string and stimulation equipment within the wellbore, it may be desirable to “pressure test” the casing string and stimulation equipment, to ensure the integrity of both, for example, to ensure that a hole or leak has not developed during placement of the casing string and stimulation equipment. Pressure-testing generally involves pumping a fluid into an axial flowbore of the casing string such that a pressure is internally applied to the casing string and the stimulation equipment and maintaining that hydraulic pressure for sufficient period of time to ensure the integrity of both, for example, to ensure that a hole or leak has not developed. To accomplish this, no fluid pathway out of the casing string can be open, for example, all ports or windows of the fracturing equipment, as well as any additional routes of fluid communication, must be closed or restricted.
Following the pressure test, it may be desirable to provide at least one route of fluid communication out of the casing string. Conventionally, the methods and/or tools employed to provide fluid pathways out of the casing string after the performance of a pressure test are configured to open upon exceeding the pressure levels achieved during pressure testing, thereby limiting the pressures that may be achieved during that pressure test. Such excessive pressure levels required to open the casing string may jeopardize the structural integrity of the casing string and/or stimulation equipment, for example, by requiring that the casing and/or various other wellbore servicing equipment components be subjected to pressures near or in excess of the pressures for which such casing string and/or wellbore servicing component may be rated. Thus, a need exists for improved pressure testing valves and methods of using the same.